The US-led invasion of Iraq in 2003 spurred multiple different regional outcomes. Primarily, the US invasion led to the rise in sectarianism that spread across the region after the ensuing war. In Iraq the Sunni Shia divide in domestic politics created heightened tensions across the region. This was caused by the after effects of the overthrow of the Iraqi government  and the election of a new ruling party that highlighted the sectarian divides. Additionally, this created an opportunity for outside powers such as Iran and Iraq meddling in internal Iraqi affairs. Aside from the Iran-Saudi competition, other actors, whether they be state or non-state actors, began to see a rise in the broader Middle East. For example, the evolution of smaller terrorist groups into the Islamic State was born out Iraqi sectarian violence and later spread to other  countries in the region. The presence of non-state actors in the region is one of the largest reasons for consistent outside presence in the Middle East. This has included the rise in United States military long standing presence and its label as the security hegemon in the region. Additionally, the fall of Iraq in terms of power politics provided an opportunity for Iran to rise into the role of the dominant state in the region. This has included its ability to now export its ideas to Iraq, but also grow its regional presence as the Middle East shifts towards  bipolarity.

Furthermore, the US-led invasion created a sense of insecurity within the government of Saudi Arabia which had tangible effects with neighboring nations such as Yemen. Yemen itself has a longstanding history of sectarian violence between Islamic groups and this has only been exacerbated by Saudi and US interference in the ongoing Civil War. Overall, US-led invasion had widespread unintended consequences that devastated the region in multiple ways outside of simply the Saudi-Iran power struggle.